Composition of improved water-glycol antifreeze and heat exchange media and process for manufacture of same



COMPOSITION OF IMPROVED WATER-GLYCOL ANTIFREEZE AND HEAT EXCHANGE MEDIAAND PROCESS FOR MANUFACTURE OF SAME Matthew A. Boehmer, Allen Park,Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., acorporation of Michigan No Drawing. Continuation-impart of applicationSer. No. 452,354, Apr. 30, 1965. This application Oct. 12, 1967, Ser.No. 674,715

Int. Cl. C09k 3/02 U.S. Cl. 25275 6 Claims ABSTRACT OF THE DISCLOSURE Aliquid composition suitable for use in aqueous liquid heat exchange-typecooling systems for internal combustion engines consisting essentiallyof about 90 to 96 weight percent dihydroxyaliphatic alkanol having about2 to 6 carbon atoms, about 0.5 to 3.0 weight percent alkali metalorthophosphate, about 0.1 to 3.0 weight percent alkali metal borate,about 0.1 to 1.0 weight percent mercaptobenzothiazole compound, andabout 0.05 to 0.5 weight percent Water-soluble complex phosphatedepicted by the general formula, A Z P O wherein A is alkali metal, Z isselected from the group consisting of zinc and magnesium, P isphosphorous, O is oxygen, x is about 2 to 3.8, y is about 0.1 to 1.0,the ratio x/y is about 2 to 3.8, v is. about 7 to 10, w is about 2 to 3and the ratio v/w is about 3.3 to 3.8, and sufiicient minor amount ofwater necessary to effectively dissolve the components.

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 452,354, filed Apr. 30, 1965.

This invention relates to alcoholic antifreeze compositions suitable foruse in aqueous liquid heat exchange cooling systems and, moreparticularly, for internal combustion engine cooling systems.

As is well known to those skilled in the art, glycolbased antifreezecompositions for use in heat exchange systems, and particularlyautomotive cooling systems, possess definite advantages as compared withvolatile antifreeze compositions employing lower aliphatic alcohols.However, these glycol-based antifreeze compositions require compoundingwith corrosion inhibitors, antifoam additives, and other compatibleadditives to prevent the corrosion of metals and the foaming of thesolution obtained by diluting the antifreeze with various potablewaters. It is Well known that the metal parts in the cooling systems ofinternal combustion engines often comprise iron, copper, brass, solder,steel and aluminum. Due to the variety of metals used and variedresulting metal combinations, the long-term prevention of corrosion onall metals is particularly difficult because of galvanic cells, additiveinteraction and depletion.

The prior art has suggested the use of many types of corrosioninhibitors among which may be mentioned borax, arsenites,triethanolamine, sulfonated oils, resinates, sodium nitrite, sodiumbenzoate, triethanol ammonium phosphate, mercaptobenzothiazole andalkali metal mercaptobenzothiazole, maleic acid, picric acid,bolybdates, tungstates, urea, naphthenates, etc., which are used eitheralone or in combinations.

The inhibitors, known up to now, differ to a rather considerable degreeas to their effect in connection with various metallic materials. Thus,there are known inhibitors which give a maximum effect in connectionwith light metals (for example, in cylinder heads) while others are moresuited for nonferrous, heavy metals such as 3,445,395 Patented May 20,1969 copper, and their alloys (for example, in heat exchangerconstructions), and again others are relatively well suited for ferrousmetal castings (for example, in motor blocks). It it, therefore, aproblem to find an inhibitor or combination thereof which gives thegreatest possible protective effect for the combinations of iron-likemetals, light metals such as aluminum, heavy non-ferrous metals such ascopper and alloys of such metals. While the inhibitors discussed aboveare suitable for many uses, they present serious problems where highspeed, that is, high rpm. aluminum alloy cooling fluid pumps areemployed. It has been found that where high r.p.m. aluminum alloycooling liquid pumps are employed in the system that, in general, theantifreeze compositions employing the above inhibitors do not meet theperformance requirements of the automobile industry.

Accordingly, it is a purpose of this invention to provide a liquidantifreeze composition which is suitable for use in aqueous liquid heatexchange-type cooling systems for internal combustion engines whereinsaid aqueous liquid is circulated by a high r.p.m. aluminum alloy pumpand which composition is not detrimental to other parts of theconventional cooling system.

The foregoing and other objects of the invention are achieved by aliquid composition suitable for mixing with water which includes aboutto 96 weight percent dihydroxy aliphatic alcohol having about 2 to 6carbon atoms, about 0.5 to 3.0 weight percent alkali metalorthophosphate, about 0.1 to 3.0 weight percent alkali metal borate,about 0.1 to 1.0 Weight percent of mercaptobenzothiazole compound, about0.05 to 0.5 weight percent water-soluble complex phosphate depicted bythe following general formula, A Z P O wherein A is alkali metal, Z isselected from the group consisting of zinc and magnesium, P isphosphorous, O is oxygen, x is about 2 to 3.8, y is about 0.1 to 1.0,the ratio x/y is about 2 to 3.8, v is about 7 to 10, w is about 2 to 3and the ratio v/w is about 3.3 to 3.8, and sufficient minor amount ofwater necessary to efliciently dissolve the additives.

The composition of this invention is preferably prepared by preparing asolution of a zinc or magnesium compound, or both, and alkali metalpyrophosphates or polyphosphates, or both, and a solution of theremaining components and then combining the two solutions. The zincand/or magnesium compounds react with the pyrophosphate and/orpolyphosphate to produce the compound having the formula, A Z P O' setforth above. More specifically, by way of illustration, when the zinccompound is zinc nitrate and the pyroor polyphosphate is potassiumpyrophosphate, the reaction is as follows:

Similarly, if the magnesium compound is magnesium acetate and sodiumpolyphosphate is employed, the following reaction takes place:

Mg z a z) 2 'b s ex lo" a s io 2 a 2 When the antifreeze composition isdiluted with water, a clear solution is formed, proving that theinsoluble compounds ZIlzPgOq and Mg P O- have not been formed, and thatthe complex phosphates as shown in the above formulas have been formed.In the ultimate aqueous solution the complex phosphate, e.g., K ZnP Omay ionize in the following manner:

As a source of magnesium or zinc, a wide variety of compounds obvious tothose skilled in the art may be employed, such as, for example, zincnitrate, zinc acetate, zinc trimethylolphenate, zinc thiosulphate, zincoxide, zinc fluoride, zinc iodate, zinc salicylate, magnesium acetate,magnesium arsenite, magnesium ferrocyanide, magnesium fluosilicate,magnesium nitrate, magnesium oxide, magnesium sulphate, and magnesiumthiosulphate. The alkali metal pyrophosphates and polyphosphates whichmay be employed preferably have mole ratios of oxygen to phosphorous ofabout 3.3 to 3.8. These include sodium clude mono-, di and tripotassiumorthophosphate and mono-, diand trisodium orthophosphate.

The mercaptobenzothiazole compounds which may be employed includeZ-mercaptobenzothiazole and alkali metal mercaptobenzothiazoles such assodium and potasand potassium pyrophosphate, sodium and potassium D siummercaptobenzothiazole. hexametaphosphate and sodium and potassiumtripoly- It should be pointed out that the compositions disphosphate.cussed above are concentrates and in practice are added The expressionsdihydroxyaliphatic alcohol, alkali to water in a cooling system in aquantity suflicient to metal orthophosphate, alkali metal borate andmerlower the freezing point of the final solution to thedecaptobenzothiazole compound as used herein include sired temperature.Thus, the amount of concentrate conmixtures of one or more members ofthe class defined tained in the final coolant solution depends on thedesired by the expressions. freezing point. In practice such finalcoolant solutions It has been found in accordance with this inventioncomprise about to 60 weight percent of the above that the compoundhaving the general formula, A Z P O 15 described concentrate, balancewater. Thus, the final soprovides improved corrosion protection foraluminum and lution would consist essentially of about 15 to 60 weightat the same time functions as an antifoam additive. The percentdihydroxy aliphatic alcohol, about 0.15 to 1.8 combination oforthophosphates and borates employed weight percent alkali metalorthophosphate, about 0.05 in the composition provides desirablecorrosion protecto 1.8 weight percent alkali metal borate, about 0.01 totion for many metals and controls or buffers the pH in 0.6 weightpercent of mercaptobenzothiazole compound, the range of 8 to 9 which isdesirable for long-term use about 0.007 to 0.3 weight percent of aphosphate dein cooling systems. Conventional alkaline agents such aspicted by the formula, A Z P O wherein A is alkali alkali metalhydroxides may also be included to maintain metal, Z is selected fromthe group consisting of zinc and the pH in the range of 8 to 9. Themercaptobenzothiazole magnesium, P is phosphorous, O is oxygen, x isabout compound provides good protection for corrosion of cop- 2 to 3.8,y is about 0.1 to 1.0, the ratio x/y is about 2 to per and brasssurfaces and, in addition, acts as a moderate 3.8, v is about 7 to 10, wis about 2 to 3, the ratio v/w antioxidant for the glycols. Thecombination of zinc or is about 3.3 to 3.8, and about 40 to 85 weightpercent magnesium ions in a solution with the orthophosphate, water. Inaddition, the final solution may contain about borate andmercaptobenzothiazole inhibitors provides a 0.001 to 0.1 weight percentantifoaming agent. highly desirable combination of results and isparticu- Illustrative examples of the antifreeze composition of larlyadvantageous for use where aluminum pumps are this invention are shownin Table I below. An amount of employed in the cooling system. However,it was not conventional dye is added to each solution in amount topossible to use such a composition in the prior art since impart thedesired color. The compositions of these exthe zinc or magnesium ionsnormally react with the orthoamples are obtained by preparing a separatesolution of phosphate, borate or the mercaptobenzothiazole inhibitorsthe zinc nitrate, magnesium acetate and the pyrophosphate to give anundesirable product. or polyphosphate in an amount of water of about0.25 The applicant has discovered that by including in the percent byweight of the final solution, whereby a phoscomposition a phosphatehaving the general formula phate depicted by the formula, A Z P Odescribed A Z P O set forth above, this problem is not presented. above,is obtained. A solution of the remaining compo- It is desirable for theliquid composition of this innents is prepared and these solutions arethen combined. vention to include at least one of the conventional antiThese solutions can be used as a stock solution for addifoaming agents,such as nonionic surface active agents, tion to water to provide theultimate cooling fluid.

TABLE I Percent by weight Ethylene gly 95.0 95.0 85. Diethylene glycol5. Propylene glycol 5. Dipotassium phosphate. 1 Trisodium phosphate 1. 0Sodium hydroxide, aqueous... 0. 18 0. 04 0. 1 2-mercaptobenzothlazole0.25 0.25 0.05 0.1 0.25 Sodium mercaptobenzothiazole.--.. Potassiummercaptobenzothiazole Sodium tetraborate-5-hydrate 0.36 0.36 0.5 1Sodium metaborate-8-hydrate- Tetrapotassium pyrophosphate 0.10 0.12 0.40.3 Sodium tripolyphosphate Zinc nitrate-6-hydrate-. 0.012 0.045 0Magnesium acetate i-hydrate 0.023 0.14 0.11 .09 Antifoam 0 02 0.02 0.10.1 0. 05 0.05 0.05 0.1 0.1 0.02 0. 02 Water 1 The antiioam is thepolyoxyethylene adduct of a polyoxypropylene hydrophobic baseflhaving anaverage molecular weight of about 2,500, wherein the oxyethylene contentis about 10 weight percent of the molecule.

2 Balance.

The above antifreeze solutions exhibit a specific gravity 25/25 C. ofabout 1.15, a pH of about 8.5 for the formulations shown above and pH ofabout 8-9 when diluted with water to form a 50% by volume aqueoussolution. Reserve alkalinity for 10 mls. is about 15 to 25. The freezingpoint of a 50% by volume aqueous solution is about 35 F. The equilibriumboiling point is about 340 F.

The superiority of the antifreeze composition of this invention overprior art commercial compositions is shown by the results of paralleltests which were run using antifreeze compositions of Examples 1 and 2of Table I above,

in comparison with commercial antifreeze compositions containing wellknown prior art inhibiting agents and the compositions of Table 11below.

TABLE IL-COMPOSITIONS, WEIGHT PERCENT Ethylene glycol Diethylene glycolPropylene glycol Dipotassium phosphate Sodium hydroxide, 50% aqueous2-mercaptobenzothiazole Sodium tetraborate-5-hydrat Zinc nitratehexahydrate. Magnesium acetateA-hydrate. Antiioam (same as Table I)Water Magnesium tetrabnmte 1 Balance. 1 Omit.

voir and is adjusted to give 16 to 22 inches of mercury vacuum at thepump inlet. The pump discharge pressure is controlled at 25 pounds persquare inch gauge. This set of test conditions results in severecavitation conditions within the aluminum pump. ASTM 1384-6 l-T metalcorrosion specimens are mounted in the reservoir and weight losses forthese metal specimens were determined by the ASTM 1384-61-T method andthe results are shown in Table III below. A thermostatically controlledelectric resistance heater is provided in the conduit to heat andmaintain the temperature of the solution. At the start-up of the testthe solution is maintained at about 110 F. After circulation has begunand the conditions level oif, the coolant temperature is increased to245 F. The pump is then operated for 100 hours under these conditions.The cover of the pump is removed at the completion of 100 hours and theeffect of the coolant on the pump is determined by observing thecondition, including pitting, etc., of the pump and cover thereof. Thesolution is then rated from 1 to 10 for pump cavitation and erosion asshown in Table III below.

TABLE III Rating No erosion present; no metal loss 10 Very, very light,slight smoothing or shining of pump onstrate the functionality of thiscomponent of the in- Surface 9 ventlon. In Table II, compositionNo. 3 isthe composltlon very light Slight roughness similar to sand cast a1umiof US. 3,015,629 to Truitt, and 1s exemplary of prlor art num surface 8patents on corrosion inhibited antifreeze compositions.

. 1 ht medlum rou hness over 0-15 of areara Table IV below sets forthtest results for corros1on of 3 1 ittin g 1 n 7 various metals and thecavitation and erosion of alumi- M p 57 E num circulation pumps used ininternal combustion en- 6 5 oug mess over a 0 area so eve y 6 ginesystems, with solutions of Detroit city water con- Plts or groovestaining 15% by weight of the formulations of this in- Medmm very rough(Over 50% of area) some Plts vention as well as five commercialinhibited antifreeze grooves 5 compositions and compositions 1-3 of Tabl11 b Medium-severe, plts or grooves 4 In addition, results obtained withsolutions of Examples Severe, large and p P of grooves, 110 fflllllfe 31 and 2 in ASTM 1384-61T, corrosive water, are also V ry Severe, y largep pits or grooves 2 shown. 40 Pump case leaking due to erosion 1 TABLEIV.15% ANTIFREEZE IN DETROIT CITY WATER Pump cavitation and erosionrating Corrosion losses in milligrams per square inch Cast Alu-Description Pump Cover Copper Solder Brass Steel iron minum CommercialAntifreeze A 5 6 36 25 5 0 0 6 Commercial Antifreeze B 8 8 1 11 1 0 0 54Commercial Antifreeze C- 3 4 2 27 1 0 0 89 Commercial Antifreeze D 3 454 29 3 0 0 17 Commercial Antifreeze E".-. 3 5 1O 13 4 1 1 16Composition 1 (Table II)- 6 8 1 10 1 .5 0 .5 1 17 I) 8 8 1 7 1 1 1 10 1o10 1 1 1 1 1 10 Ex. 1 (Table I) compositio 10 10 0 2 1 0 0 1 Ex. 2(Table I) composition--. 10 10 0 6 1 0 l 2 Antlfreezes Diluted with ASTM1384-61-T Corrosive Water Ex. 2 (Table I) composition I at cone. inwater containing 100 ppm. ea. of chloride, sulfate, and bicarbonate 1010 1 0 2 0 0 2 Ex. 2 (Table I) composition at 15% cone. in water containing 100 p.p.m. ea. of chloride, sulfate, and bicarbonate 9 10 0 8 11 3 3 The apparatus for the test consists of a standard automotivealuminum water pump having a capacity of 56 gallons per minute whichrotates at a speed of 5000 rpm. and a cast metal reservoir about 10inches in diameter by 12 inches high. The discharge and suction of thepump are connected by a circulation conduit of brass tubing and fittingsand rubber hose whereby the antifreeze solution may be circulated fromthe discharge of the pump through the circulation conduit, the reservoirand back to the suction of the pump. A restrictive inch diameter orificeis installed at the pump inlet. An adjustable flow control While therehas been shown and described hereinabove the present preferredembodiments of this invention, it is to be understood that variouschanges, alterations, and modifications can be made thereto withoutdeparting from the spirit and scope thereof as defined in the appendedclaims.

What is claimed is:

1. A liquid composition suitable for use in aqueous liquid heatexchange-type cooling systems for internal combustion engines consistingessentially of about 90 to 96 weight percent dihydroxyaliphatic alkanolselected valve is placed between the pump discharge and the reserfromthe group consisting of ethylene glycol, diethylene glycol, propyleneglycol and mixtures thereof, about 0.5 to 3.0 weight percent alkalimetal orthophosphate, about 0.1 to 3.0 weight percent alkali metalborate, about 0.1 to 1.0 weight percent of a compound selected from thegroup consisting of mercaptobenzothiazole and alkali metalmercaptobenzothiazoles, and about 0.05 to 0.5 weight percentwater-soluble complex phosphate depicted by the general formula: A Z P Owherein A is alkali metal, Z is selected from the group consisting ofzinc and magnesium, P is phosphorous, O is oxygen, x is about 2 to 3.8,y is about 0.1 to 1.0, the ratio x/y is about 2 to 3.8, v is about 7 to10, w is about 2 to 3 and the ratio v/w is about 3.3 to 3.8, andsuflicient minor amount of water necessary to effectively dissolve thecomponents.

2. The composition of claim 1 wherein said alkali metal borate is thetetraborate of a metal selected from the group consisting of sodium andpotassium.

3. The composition of claim 1 which includes about 0.001 to 0.2 weightpercent antifoaming agent selected from the group consisting of nonionicsurface active agents, silicone antifoam agents, aliphatic alcohols of10 carbons or more, organic phosphates and phthalates.

4. A liquid composition suitable for use in aqueous liquid heatexchange-type cooling systems for internal combustion engines consistingessentially of about 90 to 96 weight percent dihydroxyaliphatic alcoholselected from the group consisting of ethylene glycol, diethyleneglycol, propylene glycol and mixtures thereof, from about 0.5 to 3.0weight percent alkali metal orthophosphate selected from the groupconsisting of monopotassium phosphate, dipotassium phosphate,tripotassium phosphate, monosodium phosphate, disodium phosphate,trisodium phosphate and mixtures thereof, about 0.1 to 3.0 weightpercent alkali metal borate, about 0.1 to 1.0 weight percent of acompound selected from the group consisting of mercaptobenzothiazole,sodium mercaptobenzothiazole and potassium mercaptobenzothiazole, about0.05 to 0.5 weight percent of a Water-soluble complex phosphate obtained by mixing in aqueous solution a phosphate selected from the groupconsisting of alkali metal pyrophosphates, alkali metal polyphosphatesand mixtures thereof with about 0.001 to 0.10 weight percent of cationsobtained by the inclusion in the composition of compounds selected fromthe group consisting of zinc nitrate, zinc acetate, zinctrimethylolphenate, zinc thiosulfate, zinc oxide, zinc fluoride, zinciodate, zinc salicylate, magnesium acetate, magnesium arsenite,magnesium ferro cyanide, magnesium fluosilicate, magnesium nitrate,magnesium oxide, magnesium sulfate and magnesium thiosulfate, and about0.5 to 5 Weight percent water.

5. An aqueous coolant fluid for use in heat exchangetype cooling systemsfor internal combustion engine consisting essentially of about 15 toweight percent dihydroxyaliphatic alkanol selected from the groupconsisting of ethylene glycol, diethylene glycol, propylene glycol andmixtures thereof, about 0.15 to 1.8 weight percent alkali metalorthophosphate selected from the group consisting of monopotassiumphosphate, dipotassium phosphate, tripotassium phosphate, monosodiumphos phate, disodium phosphate, trisodium phosphate and mixturesthereof, about 0.05 to 1.8 weight percent of alkali metal borate, about0.01 to 0.6 weight percent of a compound selected from the groupconsisting of mercaptobenzothiazole and alkali metalmercaptobenzothiazoles, about 0.007 to 0.3 weight percent of awater-soluble complex phosphate depicted by the following formula: A Z PO wherein A is alkali metal, Z is selected from the group consisting ofzinc and magnesium, P is phosphorous, O is oxygen, x is about 2 to 3.8,y is about 0.1 to 1.0, the ratio of x/y is about 2 to 3.8, v is about 7to 10, w is about 2 to 3, the ratio v/w is about 3.3 to 3.8, and about40 to 85 weight percent water.

6. The composition of claim 5 which includes about 0.001 to 0.1 weightpercent antifoaming agent selected from the group consisting of nonionicsurface active agents, silicone antifoam agents, aliphatic alcohols of10 carbons or more, organic phosphates and phthalates.

References Cited UNITED STATES PATENTS 2,616,854 11/1943 Fenske 252792,777,821 l/ 1957 Harford 25278 2,937,145 5/1960 Cutlip et a1. 252-752,980,620 4/1961 Hatch 252 3,015,629 1/1962 Truitt 252 OTHER REFERENCESPutilova: Metallic Corrosion Inhibitors, Pergamon Press, 1960, p. 151.

LEON D. ROSDOL, Primary Examiner.

STANLEY D. SCHWARTZ, Assistant Examiner.

US. Cl. X.R. 252-78, 389

